New Delhi: Mercury hovered below normal levels in most areas of north India on Friday intensifying the winter chill even as dense fog across vast swathes led to massive disruptions in road, rail and air traffic.

Hilly areas of Himachal Pradesh and Kashmir groaned under biting cold as night temperatures dipped by several notches, while the northern plains were covered under thick fog, which affected services of nearly 100 trains and dozens of flights.

The national capital, however, witnessed a pleasant day as a chilly morning gave way to bright sunshine, pushing the maximum temperature up to 20 degrees Celsius, normal for this time of the year.

The minimum temperature also rose significantly with it being recorded a notch above the season's average at 8.2 degrees Celsius, as compared to yesterday's 5.8 degrees.

Early morning fog disrupted train and flight operations, with a total of 30 flights and 87 trains, including premier services like Rajdhani and Duronto, being delayed.

In Uttar Pradesh, several areas shivered under cold wave conditions. According to MeT officials, Nazibabad in Bijnore recorded the state's lowest temperature at 3.2 degrees. Fog shrouded vast swathes of the state affecting normal life.

The Lucknow district administration, in view of extreme cold, has ordered closure of all schools up to Class VIII till January 21. "For Classes IX to XI, schools will remain open but the timings will be from 11 am to 2 pm," Lucknow District Magistrate Rajshekhar told PTI.

Meanwhile, winter intensified its grip over Rajasthan with mercury falling by one to two degrees in most places.

According to the MeT department, the state's sole hill station, Mount Abu, recorded the lowest temperature of the season at 1 degree Celsius last night. Minimum temperatures at Pilani, Churu, Sriganganagar and Kota were recorded at 4.2, 5.2, 6 and 6.2 degrees Celsius, respectively.

Dense fog disrupted movement of trains and road transport in the state throwing normal life out of gear. About a dozen trains were running late and five others were re-scheduled, according to a North Western Railway (NWR) spokesman.

Cold wave also continued unabated in Punjab and Haryana. Narnaul in Haryana was the coldest place in both the states as it recorded a minimum temperature of 3.1 degrees Celsius, two notches below normal. Amritsar in Punjab shivered at 3.5 degrees while Chandigarh registered a low at 5.8 degrees.

Several trains were running late and two flights from Bangalore and Delhi to Chandigarh were cancelled due to foggy weather conditions.